DIY Cost Tools
Pool Fill Time Calculator
HOME & OUTDOOR PLANNING
Estimate pool or tank filling time from added volume, measured flow, and expected average flow.
Use the units shown. All fields are required; absolute values cannot exceed one trillion. Assumes the stated flow is maintained on average and ignores leaks, interruptions, and pressure changes beyond your adjustment. Do not leave filling unattended; observe local water-use rules and protect against backflow.
How to use this calculator
Replace the example inputs with your own measured values, using the units beside each field. Select Calculate, then compare results under different practical assumptions. Keep extra precision in measurements until the final answer.
Formula and explanation
Effective flow = measured flow × average-flow percentage/100; time = volume ÷ effective flow
The average-flow percentage lets you allow for an expected reduction from the measured rate. If flow remains constant, use 100%.
Worked example
With Water volume to add (US gallons) = 12000, Measured flow rate (US gallons/minute) = 8, Expected average flow (%) = 90, the results are Estimated time (minutes): 1,666.6667; Estimated time (hours): 27.777778; Estimated time (days): 1.1574074; Effective flow rate (US gallons/minute): 7.2.
Important limitations
Assumes the stated flow is maintained on average and ignores leaks, interruptions, and pressure changes beyond your adjustment. Do not leave filling unattended; observe local water-use rules and protect against backflow.
These are planning estimates. Confirm actual measurements, product instructions, site conditions, and any applicable project requirements before purchase or installation.
Frequently asked questions
Should I enter total pool volume?
Enter only the volume still needed, which may be less than the full pool capacity.
How do I measure flow?
Time a known-volume container and divide its volume by the filling time in minutes. Use the same hose configuration safely.
Can I mix measurement units?
No. Convert values to the units shown beside the fields first. The result labels identify the output units.
What happens when inputs are invalid?
Blank, negative where disallowed, nonfinite, or out-of-range values clear the old results and show an instruction.
Review notes
Reviewed October 1, 2026. Default examples were checked independently against the displayed equations and conversion factors. Page-script tests covered blank, negative, nonfinite, and excessive inputs. Calculations run locally in your browser.